Steam for Linux

So far, I can reproduce this issue with 100% reliability. If I start the Steam client, switch to Big Picture mode, click on Library, and then click on Portal, the client immediately crashes ungracefully (i.e., no uploading of crash files, just an immediate crash) with a segmentation fault (invalid pointer). I searched the forum to see whether others had reported this issue, but couldn't find any duplicates. I also saved copies of the .dmp files that were created (but not uploaded) in /tmp/dumps, so I can upload those if that would be helpful; right now, I don't know the preferred way of doing so, if there is one.

Command Line Output at the time of the crash (with my username masked):